A focus detection device is per se known in which a plurality of photoreception elements are arranged to each of micro lenses that are arranged in a two dimensional pattern, and that performs focus detection by a so-called phase difference method, in which an amount of image deviation is detected on the basis of the photoreception outputs of those pluralities of photoreception elements. For example, in Patent Document #1, a focus detection device is described that eliminates false focusing upon a subject that has a periodic pattern by generating at least three signal sequences and thus obtaining a plurality of amounts of image deviation.